The present invention relates to a device for displaying a desired developing color of a copying machine capable of changing the developing color. More specifically, this invention relates to a developing color display device in which a control circuit outputs a signal corresponding to the developing color in a development cell in the copying machine to selectively turn on light emitting bodies of three primary colors (red, green and blue) and/or change the luminous intensities of the light emitting bodies according to the signal, so that a desired developing color of light is synthesized and presented on a developing color indicator.
FIG. 7 is a schematical plan view of a copying machine incorporating the conventional developing color display device. The copying machine 1 with an original cover 2 has a print switch 3, key switch 4, multi indicator 5 and developing color indicator 6. The developing color indicator 6 is composed of three display windows for blue, red and black. When additional developing colors are to be used, display windows may be added by the same number as the additional colors. Each display window is provided with a light emitting body such as an LED that emits a specific color of light so that, when a development cell of a particular color is loaded in the copying machine, only the light emitting body of this particular color is turned ON with the rest of the colors remaining OFF.
As described above, the conventional developing color display device is required to indicate developing colors independently and therefore involves an increased number of parts. There is no problem when the copying machine uses two or three developing colors. With 8 to 16 developing colors, however, the cost rises and at the same time the display space requirement increases accordingly, which is not desirable when producing a compact copying machine.